1. Field of the Invention
The methods and apparatus taught in the present application relate generally to the field of noise reduction in a computer system. Specifically, the present invention teaches a component enclosure that provides improved noise reduction.
2. Art Background
Typical prior art computer enclosure designs are driven by three primary goals: to provide a proper thermal operating environment for the components; to minimize the size of the enclosure; and to minimize the acoustic signature of computer system to nearby observers. However, by practical necessity, computer enclosures must at least minimally meet the thermal goal because system failure can occur if the system components operate at a temperature beyond the specified operating temperature. In order to provide a proper thermal operating environment, the enclosure is typically designed to support the operation of a cooling system that uses a fan to provide a steady flow of air across the components. This typically results in the enclosure having a number of air vents or slots cut into its side walls.
The use of a fan cooling system increases the acoustic signature of the computer system because the operation of the fan produces noise, which escapes to the numerous slots and vents in the enclosure. Thus, computer enclosure design is often a compromise between the thermal goal and the noise goal. For example, a designer can use foam or some form of passive noise reduction. However, the foam is bulky, potentially increasing the footprint of the enclosure, and the foam will block air flow through the slots and vents, compromising the thermal goal. A second option is to reduce the acoustic signature of the fan in order to produce a corresponding reduction in the acoustic signature of the enclosure. This typically requires running the fan at a voltage that is below the optimum operating voltage of the fan, or it may require the use of a smaller fan. The thermal goal is then compromised.
The result is often a design that meets the acoustic goal only to the extent that the thermal goal can be compromised. Thus, typical designs diminish the cooling capacity of the cooling system in order to reduce the acoustic signature only slightly. Recent advances in integrated circuit design are increasing the difficulty of designing an adequate computer enclosure.
Modern manufacturing processes allow a more dense population of transistors in the same die space, leading to integrated circuit chips that run hotter than previous chips. Therefore, more cooling is required. One solution to meeting the thermal goal is to increase the size of the fan in order to move more air across the components. Of course, this solution has an impact on the goals to minimize the acoustic signature and the physical size of the enclosure. This leads to the counterintuitive result that as chip size decreases, the size of the enclosure increases.
The compromises inherent in prior art enclosure designs are becoming unacceptable, and a new approach to computer enclosure design is needed. Therefore, as will be described, the method and apparatus of the present invention disclose a two phase approach to enclosure design in which the thermal goal and the acoustic goal are addressed substantially in isolation. More particularly, there is disclosed a thermal box that has a limited number of well-defined openings to which are attached acoustic ducts that combine passive and active noise cancellation techniques to reduce the acoustic signature of the enclosure.